Soiled human hair is shampooed to remove sebum that is naturally secreted by the head, as well as soil and other atmospheric contaminants that accumulate on the hair. Sebum, in particular, accumulates on the hair in a relatively short period of time leaving the hair with a greasy, dirty feel and poor manageability. The most effective shampoos for cleansing the hair for removal of the atmospheric contaminants and sebum are those that contain high lather synthetic anionic detergents, such as the long-chain alkyl sulfates and the partially ethoxylated long-chain alkyl sulfates. These synthetic anionic detergents are very effective for cleansing the hair but, after rinsing with water, leave the hair with a dried touch, usually called "creak" and result in hair, when wet, that is in an extremely tangled and unmanageable after-shampoo condition.
Thoroughly cleansed hair is extremely difficult to comb in either the wet or dry state because the individual hair fibers tend to snarl, kink, and interlock with each other. Particularly prior to complete drying of thoroughly cleansed hair in this after-shampoo stage the hair is very difficult to comb or brush. Even after complete drying, the thoroughly cleansed hair remains difficult to comb or brush and does not set well. Thoroughly clean, dried hair also has undesirable electrostatic properties in a low humidity atmosphere that causes the hair to "fly away," thereby further reducing the combing or brushing property of the hair. Generally, these above-outlined problems that result from synthetic detergent cleansing of the hair, particularly the high-lather synthetic anionic detergents, have been elevated either by the after-shampoo treatment of the hair with hair conditioners, for example in the form of a hair rinse, or by including hair conditioners directly within the shampoo composition.
After-shampoo hair conditioning compositions are easily formulated but are inconvenient to use because of the necessity of applying the conditioner to the hair in a separate stage after shampooing. The preparation of a conditioning shampoo has been more difficult because of inherent incompatibility problems between anionic surfactants and the fatty cationic compounds that are good conditioning agents. Contact between an anionic surfactant and a cationic surfactant or cationic polymer produces a precipitate that forms immediately or causes an interaction between the anionic and cationic compounds that significantly reduces their respective cleaning and conditioning properties. The reduction in cleansing and conditioning effectiveness is observed even in compositions wherein the anionic and cationic compounds do not precipitate from the composition but remain in solution or suspension. This incompatibility between an anionic surfactant and a cationic conditioning compound is well recognized by those skilled in the art. For example, Safarin in Cosmetics, Interscience Publishers, Inc., New York, p. 538 (1957), states that anionic and cationic compounds cannot be used in combination because they react to form insoluble salts.
A partial solution to this incompatibility problem in the formulation of conditioning shampoos is exemplified by the following patents that disclose compositions that contain surfactants that are not anionic, e.g., nonionics, amphoterics and zwitterionics, together with cationic conditioning compounds: U.S. Pat. No. 3,849,348 to Hewitt; U.S. Pat. No. 3,990,991 to Gerstein; and U.S. Pat. No. 3,822,312 to Sato. Published European Patent Application EP 0 407 042 A2 teaches long-chain alcohols, long-chain ethoxylated alcohols and/or long-chain esters or acids in conditioning shampoos.
Another problem inherent in formulating a conditioning shampoo is an instability problem that results when water-insoluble conditioning agents are also included in the conditioning shampoo composition, such as the non-volatile silicones that are well recognized in the art as providing a degree of softness to the hair.
Silicones in shampoo compositions have been disclosed in a number of different patents: U.S. Pat. No. 2,826,551, Mar. 11, 1958 to Green; U.S. Pat. No. 3,964,500, Jun. 22, 1976 to Drakoff; U.S. Pat. No. 4,364,837, Dec. 21, 1982 to Pader; British Patent No. 849,433, Sep. 28, 1960 to Woolston; U.S. Pat. No. 4,741,855 to Grote et al.; U.S. Pat. Nos. 4,788,006 and 4,902,449 to Bolich, Jr. et al.; and U.S. Pat. No. 4,704,272 to Oh et al.
A particularly difficult problem to solve in silicone-containing conditioning shampoos is that of keeping a dispersed, water-insoluble, non-volatile silicone material suspended in stable form while retaining the cleansing, particularly foam volume, and conditioning performance of the conditioning shampoo. A variety of materials have been proposed for inclusion in silicone-containing conditioning shampoos for purposes of thickening and stabilization such as xanthan gum, long-chain acyl derivatives, long-chain amide oxides, and long-chain alkanolamides as disclosed in U.S. Pat. Nos. 4,788,006, 4,704,272, and 4,741,855. The compositions of the present invention are stable and have increased foam volume and conditioning properties without amine oxide or acyl derivative suspending agents.